First-principles study of the structural, phonon, elastic, and thermodynamic properties of Al_3Ta compound under high pressure

We have investigated the phonon, elastic and thermodynamic properties of L1$_{2}$ phase Al$_{3}$Ta by density functional theory approach combining with quasi-harmonic approximation model. The results of phonon band structure shows that L1$_{2}$ phase Al$_{3}$Ta possesses dynamical stability in the pressure range from 0 to 80 GPa due to the absence of imaginary frequencies. The pressure dependences of the elastic constants $C_{ij}$, bulk modulus $B$, shear modulus $G$, Young's modulus $Y$, $B/G$ and Poisson's ratio $\nu$ have been analysed. The elastic constants are satisfied with mechanical stability criteria up to the external pressure of 80 GPa. The results of the elastic properties studies show that Al$_{3}$Ta compound possesses a higher hardness, improved ductility and plasticity under higher pressures. Further, we systematically investigate the thermodynamic properties, such as the Debye temperature $\Theta$, heat capacity $C_{p}$, and thermal expansion coefficient $\alpha$, and provide the relationships between thermal parameters and pressure.